The present invention generally relates to apparatus and methods of sealing surfaces to one another. More particularly, the present invention relates to apparatus and methods that allow for the use of standard O-rings that can seal static surfaces under changing conditions such as high temperature and pressure exposure.
In a variety of environments, two static surfaces oftentimes need to be sealed to one another. For example, compressors in vapor cycle systems of environmental control systems need to be hermetically sealed to prevent the escape of refrigerants. Currently, elastomer O-rings provide hermetic seals but they permanently set after exposure to high temperature and clamp load during operation. Consequently, refrigerant leakage occurs after a relatively short period of time. Leakage is aggravated by the movement of mating sealing surfaces when the compressor is under temperature and pressure. Of course, leakage leads to less than optimal performance. And the need to change O-rings leads to higher maintenance costs.
Numerous efforts have been made to improve sealing between static surfaces and between dynamic surfaces. One example of an effort to seal pipes inserted into holes in members such as manholes is found in U.S. Pat. No. 4,199,157. To prevent seal blowout, a two part sleeve gasket fits between the pipe and the hole. A first part of the gasket includes a tubular body portion that contacts the pipe and an outwardly curved flange radially spaced from the body portion and that contacts the hole. The second part of the gasket includes an O-ring that surrounds the body portion in the radial space defined by the flange. The cross-section of the O-ring is greater than the free radial space between the flange and the body portion so that the flange and body portion are expanded into engagement with the pipe and hole. A disadvantage to this design is its complexity, as well as the need for multiple parts. This design requires a specially shaped component that will be more expensive to fabricate compared to a standard O-ring seal. Also, this design will eventually leak when the elastomeric component permanently sets under pressure and/or temperature over time.
Another example of attempting to prevent seal blowout in the context of sealing a cylinder within a bore is found in U.S. Pat. No. 5,603,511. A seal element is moved from one axial position, up a ramp, and to a second axial position. In the second position, the seal assembly expands to contact the inside of the bore. An anti-extrusion element also contacts the inside of the bore and the seal element to prevent blowout of the seal element. The complex design of having to move the seal, however, presents a disadvantage and would not be practical to employ in varying applications. Specially designed components and complexity of assembly also make this design expensive and cumbersome to use, especially if the part needs to be reworked and the seal replaced.
In U.S. Pat. No. 4,614,348, a two component seal is provided for a fluid coupling in a pressurized fluid system having male and female parts. The male part includes a recess having a somewhat rectangular configuration. One part of the seal is an annular body having a U-shaped cross-section that defines a recess. The annular body fits within the recess of the male part such that the two extended portions of the annular body face towards the male part. The second part of the seal is an O-ring that fits within the recess of the annular body. Thereby, the O-ring sealingly engages the recess of the male part. Again, a disadvantage to this design is its complexity, the need for multiple parts, and the absence of addressing the effects of seal permanent set. Also, multiple parts and the use of specially shaped components make this part expensive.
FIG. 1 depicts a prior art design found, for example, in a compressor 10. For purposes of illustration, the compressor 10 may include a first component 11 and a second component 12 that interface one another. The first component 11 includes a first seal surface 13 and the second component 12 includes a second seal surface 14. With the first and second components juxtaposed to one another, a leakage inlet 15 may allow pressure to pass between the components 11, 12 and exit through a leakage outlet 16. To prevent such leakage, the first component 11 has a recess 17 with a substantially rectangular cross section. Accordingly, each of the walls of the recess 17 is substantially planar. An O-ring 18 is disposed in the recess to block the flow of pressure from the leakage inlet 15 and to the leakage outlet 16. As described above, however, this design is susceptible to pressure leakage over time, particularly when the compressor 10 is subject to high pressure, high temperature, and movement of the first and second seal surfaces 13, 14.
A variation of the design in FIG. 1 is shown in U.S. Pat. No. 4,477,223 for a rotating shaft within a bore of a compressor. A non-rotating ring is disposed between the shaft and bore. An annular recess in the ring has an arcuate cross section. The annular recess interfaces a recess in the bore and has a rectangular cross section. An O-ring is held between the two recesses where one of the recesses is offset to deform the ring causing it to exert an axial force on a non-rotating cylinder against a rotating ring. This seal arrangement uses the O-ring to force a stationary part against a rotating part to effect the seal between the stationary and rotating parts. Furthermore, it does not take into consideration the eventual setting of the O-ring which will eventually render the seal ineffective.
As can be seen, there is a need for an improved apparatus and method of sealing surfaces together. A further need is for an apparatus and method that not only provides sealing but is simple in design and minimizes manufacturing costs. Yet another need is for an apparatus and method that can be implemented into existing components with limited changes to the design of such components. A still further need is for an improved method and apparatus that prevents leakage between mating surfaces over extended periods of time. An apparatus and method are needed that can block leakage between mating surfaces under conditions of high pressure, high temperature and movement of the mating surfaces.
In one aspect of the present invention, a method of sealing at least a first seal surface to a second seal surface comprises the steps of placing a flexible ring member between the first and second seal surfaces; juxtaposing the first and second seal surfaces; and creating a plurality of spaced apart pressure points in the first and second seal surfaces such that the pressure points contact the ring member.
In another aspect of the present invention, a seal surface for interfacing a flexible ring member comprises a recessed area having a plurality of recesses into which the ring member can expand; and a plurality of spaced apart pressure points in said recesses that contact the ring member.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.